delete should force-stop running instances when a regular stop isn't enough

[ricab]

Describe the bug
If multipass can't stop an instance normally, it will keep running even after deleted.

To Reproduce

1. multipass shell
2. inside the instance:
   1. sudo fsfreeze --freeze /
   2. sudo ip link set ens3 down
3. back outside, multipass stop
4. observe the instance still running after the command exits (which, by the way...)
5. multipass delete primary
6. pgrep -fa qemu and observe the process still running
7. multipass recover primary
8. multipass list observe primary still running

Expected behavior
Delete would kill the instance if regular stopping did not work.

Additional info

• OS: Linux
• multipass version 1.12.0-dev.123+gdc4cbef6
• multipass get local.driver QEMU

Additional context
This should be fixable by force-stopping after #1909 is in.

[sharder996]

This is also closely related to #2492 and may be addressed by #1946. That PR might need some work to make sure its inline with what we want, but it should be a good starting point.

[mklueh]

I've had the problem that all Multipass commands were freezing.

Uninstalling was also impossible and I had two Vmmem processes with a permanent CPU load of 13% each which did not go away.

Disabling hyper-v and rebooting my virtual machine solved this issue and I was able to uninstall it.

[ricab]

This should be taken care of now.